diff --git a/testkit/src/main/java/name/remal/gradle_plugins/toolkit/testkit/functional/AbstractGradleFile.java b/testkit/src/main/java/name/remal/gradle_plugins/toolkit/testkit/functional/AbstractGradleFile.java
index 2ce5cd08..fae69599 100644
--- a/testkit/src/main/java/name/remal/gradle_plugins/toolkit/testkit/functional/AbstractGradleFile.java
+++ b/testkit/src/main/java/name/remal/gradle_plugins/toolkit/testkit/functional/AbstractGradleFile.java
@@ -146,9 +146,8 @@ public final Set<String> getAppliedPlugins() {
     }
 
     public final boolean isPluginApplied(String pluginId) {
-        val appliedPlugins = getAppliedPlugins();
-        return appliedPlugins.contains(pluginId)
-            || appliedPlugins.contains("org.gradle." + pluginId);
+        return pluginToVersion.containsKey(pluginId)
+            || pluginToVersion.containsKey("org.gradle." + pluginId);
     }
 
 }
diff --git a/testkit/src/main/java/name/remal/gradle_plugins/toolkit/testkit/functional/GradleProject.java b/testkit/src/main/java/name/remal/gradle_plugins/toolkit/testkit/functional/GradleProject.java
index f9e77088..9a80f70d 100644
--- a/testkit/src/main/java/name/remal/gradle_plugins/toolkit/testkit/functional/GradleProject.java
+++ b/testkit/src/main/java/name/remal/gradle_plugins/toolkit/testkit/functional/GradleProject.java
@@ -573,6 +573,7 @@ private GradleRunner createGradleRunner(File projectDir, boolean withConfigurati
                 "--warning-mode=all",
                 "-Dorg.gradle.parallel=true",
                 "-Dorg.gradle.workers.max=4",
+                "-Dorg.gradle.kotlin.dsl.allWarningsAsErrors=true",
                 "-Dmaven.repo.local=" + new File(projectDir, ".m2").getAbsolutePath(),
                 "-Dorg.gradle.vfs.watch=false",
                 "-Dorg.gradle.daemon=false",
diff --git a/toolkit/src/main/java/name/remal/gradle_plugins/toolkit/ComponentIdentifierUtils.java b/toolkit/src/main/java/name/remal/gradle_plugins/toolkit/ComponentIdentifierUtils.java
index 9e63bf0b..fbc07be5 100644
--- a/toolkit/src/main/java/name/remal/gradle_plugins/toolkit/ComponentIdentifierUtils.java
+++ b/toolkit/src/main/java/name/remal/gradle_plugins/toolkit/ComponentIdentifierUtils.java
@@ -6,10 +6,12 @@
 import javax.annotation.Nullable;
 import lombok.NoArgsConstructor;
 import lombok.val;
+import name.remal.gradle_plugins.toolkit.annotations.ReliesOnInternalGradleApi;
 import name.remal.gradle_plugins.toolkit.reflection.TypedMethod0;
 import org.gradle.api.artifacts.component.ComponentIdentifier;
 import org.gradle.internal.component.local.model.OpaqueComponentIdentifier;
 
+@ReliesOnInternalGradleApi
 @NoArgsConstructor(access = PRIVATE)
 public abstract class ComponentIdentifierUtils {
 
diff --git a/toolkit/src/main/java/name/remal/gradle_plugins/toolkit/DependencyUtils.java b/toolkit/src/main/java/name/remal/gradle_plugins/toolkit/DependencyUtils.java
index 36bac653..4d51075c 100644
--- a/toolkit/src/main/java/name/remal/gradle_plugins/toolkit/DependencyUtils.java
+++ b/toolkit/src/main/java/name/remal/gradle_plugins/toolkit/DependencyUtils.java
@@ -7,6 +7,7 @@
 import javax.annotation.Nullable;
 import lombok.NoArgsConstructor;
 import lombok.val;
+import name.remal.gradle_plugins.toolkit.annotations.ReliesOnInternalGradleApi;
 import org.gradle.api.artifacts.Dependency;
 import org.gradle.api.attributes.AttributeContainer;
 import org.gradle.api.attributes.HasAttributes;
@@ -74,6 +75,7 @@ private static boolean hasCategory(AttributeContainer attributes, String categor
     }
 
 
+    @ReliesOnInternalGradleApi
     public static boolean isGradleEmbeddedDependency(@Nullable Dependency dependency) {
         return Optional.ofNullable(dependency)
             .filter(SelfResolvingDependencyInternal.class::isInstance)
@@ -83,6 +85,7 @@ public static boolean isGradleEmbeddedDependency(@Nullable Dependency dependency
             .isPresent();
     }
 
+    @ReliesOnInternalGradleApi
     public static boolean isEmbeddedGradleApiDependency(@Nullable Dependency dependency) {
         return Optional.ofNullable(dependency)
             .filter(SelfResolvingDependencyInternal.class::isInstance)
@@ -92,6 +95,7 @@ public static boolean isEmbeddedGradleApiDependency(@Nullable Dependency depende
             .isPresent();
     }
 
+    @ReliesOnInternalGradleApi
     public static boolean isEmbeddedGradleTestKitDependency(@Nullable Dependency dependency) {
         return Optional.ofNullable(dependency)
             .filter(SelfResolvingDependencyInternal.class::isInstance)
@@ -101,6 +105,7 @@ public static boolean isEmbeddedGradleTestKitDependency(@Nullable Dependency dep
             .isPresent();
     }
 
+    @ReliesOnInternalGradleApi
     public static boolean isEmbeddedLocalGroovyDependency(@Nullable Dependency dependency) {
         return Optional.ofNullable(dependency)
             .filter(SelfResolvingDependencyInternal.class::isInstance)